Mars rover Curiosity drives backward to test its skills and wheels

Mars rover Curiosity shadow

JPL-Caltech/NASA

NASA's Mars rover Curiosity caught its own shadow in this image taken just after completing a backward drive of 329 feet Feb. 18. The rover drove the distance in reverse to test a method to reduce damage to its wheels.

NASA's Mars rover Curiosity caught its own shadow in this image taken just after completing a backward drive of 329 feet Feb. 18. The rover drove the distance in reverse to test a method to reduce damage to its wheels. (JPL-Caltech/NASA)

Unimpressed by Michael Jackson’s iconic moonwalk? How about a "Marswalk"? NASA’s Curiosity rover showed off its fancy footwork on the Red Planet this week by driving backward. The Mars Science Laboratory robot just finished its longest drive in three months, and it did so in reverse, riding 329 feet, reaching a total of 3.24 miles since its 2012 touchdown in Gale Crater.

“That gave us concern," Curiosity’s lead scientist and Caltech geologist John Grotzinger said at the time. "We expect to get damage to the wheels, but we were surprised at the rate.”

As it turned out, Gale Crater appears to host strangely fierce winds that are very good at sharpening rocks to little pointy pyramids, Grotzinger said. That power of erosion is potentially useful for exposing organic matter for the rover to examine, but it’s not so good for the wheels.

The researchers also think Curiosity might be more vulnerable to the rocks than its 2004 predecessors, twin rovers Spirit and Opportunity, because it’s so much bigger, and all that weight coming down on a pointy rock can do a lot more damage.

The team noticed that as the rover moved, the front and middle wheels were taking more of a beating than the rear wheels, Erickson said.

They decided to drive the rover backward, which would presumably shift the burden to the rear wheels and give the front wheels a rest. Although they thought it wouldn’t decrease the overall damage, it would even it out a bit. They tested this theory on their Mars Yard rover.

But to their surprise, the engineers also found an added bonus: Driving backward was actually reducing the total amount of damage, not just shifting the damage from the front to the back wheels.

That’s because the "rocker-bogie" system that the rover uses to drive up and over rocks uses the front wheels to put extra pressure on the rocks, sort of like getting a good toehold before you climb, to avoid slipping. But that extra pressure might not be a good idea if it’s being applied to sharpened points, over and over again.

“We realized that some of the rocker-bogie characteristics that we like in terms of mobility and our ability to go over rocks – those things work against us,” Erickson said.

But since the rocker-bogie system works only in the forward position, driving the rover backward eliminates that damaging pressure, he said.

Of course, this means there’s potentially a little more risk of it slipping on certain rocks without that pressure grip, he noted, so the trick is to know when to drive forward and when to turn it backward.

This "Marswalk" was just a test; the rover is currently driving on a soft, smooth sandy route, so there’s little need for more backward driving. The rover detoured to this path after the team realized how damaging its previous rocky route was, but it had to brave its longest dune yet, at a spot called 'Dingo Gap,' without getting stuck in the sand. That’s what happened to Opportunity at a place called Purgatory and what led to Spirit’s ultimate demise in a sand trap at a spot named Troy.

Now, the rover is heading to its next target, about half a mile away: a spot called KMS-9, now named Kimberley after an area in northwestern Australia with ancient rocks. (There’s a Down-Under theme to these names, in case “Dingo Gap” wasn’t a tip-off.) At Kimberley, the scientists hope to wield the rover’s drill if they find the right kind of rock that could yield signs of habitable environments.

Staring into the dramatic corpse of a dead star known as Cassiopeia A, astronomers using NASA's NuSTAR X-ray telescope have for the first time mapped out radioactive titanium in a supernova. Charting this astrophysical frontier, as described in the journal Nature, will help scientists...

If birds of a feather flock together, get ready to make some room. It turns out that across the animal kingdom, winged and finned creatures -- from tiny insects to giant whales – share some incredible energy-saving features in their body designs. The findings, published in Nature...

Glass may be hard, but it’s all too easy to break, as anyone who’s seen a shattered window knows. But now scientists have discovered that they can make glass 200 times tougher than normal by making it 'weaker' — using a laser to etch wavy micro-cracks into an otherwise solid...

By taking sewing thread and fishing wire and giving it a twist, scientists have created artificial muscle that’s 100 times stronger than human or animal sinew. The invention, described in the journal Science, could be useful for prosthetic limbs, humanoid robots, implanted medical devices...

Three more men have been arrested, and four others are being sought, in an investigation into "crash-and-grab" burglaries over the past few months in which thieves drove through the doors and windows of stores.

A Mundelein teenager was ordered Tuesday afternoon to remain in a juvenile detention facility at least until she’s 20 years old for the murder of her 11-year-old sister, but will be released by the time she’s 21.